# ---
# title: 1346. Check If N and Its Double Exist
# id: problem1346
# author: Tian Jun
# date: 2020-10-31
# difficulty: Easy
# categories: Array
# link: <https://leetcode.com/problems/check-if-n-and-its-double-exist/description/>
# hidden: true
# ---
# 
# Given an array `arr` of integers, check if there exists two integers `N` and
# `M` such that `N` is the double of `M` ( i.e. `N = 2 * M`).
# 
# More formally check if there exists two indices `i` and `j` such that :
# 
#   * `i != j`
#   * `0 <= i, j < arr.length`
#   * `arr[i] == 2 * arr[j]`
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: arr = [10,2,5,3]
#     Output: true
#     Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: arr = [7,1,14,11]
#     Output: true
#     Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: arr = [3,1,7,11]
#     Output: false
#     Explanation: In this case does not exist N and M, such that N = 2 * M.
#     
# 
# 
# 
# **Constraints:**
# 
#   * `2 <= arr.length <= 500`
#   * `-10^3 <= arr[i] <= 10^3`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
